The present invention relates to a golf club head and a method of making the golf club head, and more particularly to a method of adjusting the mechanical impedance of a club head to the golf ball for improving the rebound performance.
In the U.S. Pat. No. 4,928,965 filed based on the following two Japanese patent applications JP-A-61-22874 and JP-A-61-284265, the so called impedance matching theory is proposed. This theory teaches that, when the primary (1st-order) frequency of the mechanical impedance of a golf club head is matched with the primary (1st-order) frequency of the mechanical impedance of the golf ball, a loss of the energy transferred from the golf club head to the struck golf ball is reduced and, as a result, the rebound performance may be improved to increase the golf ball carry.
In the laid-open Japanese patent application JP-A-61-22874 (JP-B-4-56630), it is proposed to design a club head such that the primary frequency of the mechanical impedance of the club head falls within a frequency range of from 2500 to 4000 Hz under a state like the undermentioned strung-up free state.
In the laid-open Japanese patent application JP-A-61-284265 (JP-B-5-33071), on the other hand, it was proposed to design a club head such that the primary frequency of the mechanical impedance of the club head falls within a frequency range of from 600 to 1600 Hz under a state like the undermentioned face-fixed state.
Also in the laid-open Japanese patent application P2002-17904A, it was proposed to design a club head such that the natural vibration frequency of the club head becomes less than 600 HZ under a state like the face-fixed state.
The the present invention has realized that the mechanical impedance of a club head and frequency response function thereof vary depending on the measuring conditions and/or methods, and the present invention further studied to improve the rebound performance of a club head. As a result, optimal conditions were discovered, namely, by designing the club head to satisfy specific conditions in two different measuring methods performed under different conditions, whereby the rebound performance can be further unexpectedly improved.